This will be the third year of a comprehensive investigation of the effects of oxides of nitrogen (principally NO2) and ozone-- commonplace pollutants in urban atmospheres--on rats residing in quantitatively controlled environments. Observations are viewed in terms of their possible implications in chronic obstructive pulmonary diseases in man. Both early developmental aspects and states of advanced disease closely resembling emphysema in man are studied. The following disciplines and techniques are applied quantitatively in this program: clinical evaluation, respiratory physiology, hematology, biochemistry, labeled cell renewal, fine structural morphology by electron microscopy, gross and microscopic pathology, and postmortem pulmonary mechanics.